Indirect effects of global change accumulate to alter plant diversity but not ecosystem function in alpine tundra

1. Environmental change can affect species directly by altering their physical environment and indirectly by altering the abundance of interacting species. A key challenge at the interface of community ecology and conservation biology is to predict how direct and indirect effects combine to influence response in a changing environment. In particular, little is known about how direct and indirect effects on biodiversity develop over time or their potential to influence ecosystem function. 2. We studied how nitrogen (N), winter precipitation (snow), and warming influenced diversity and ecosystem function over six years in alpine tundra. We used path analyses to partition direct effects of environmental manipulations from indirect effects due to changes in the abundance of two dominant plants. We hypothesize that 1) indirect effects will develop more slowly but will become stronger than direct effects over time, and 2) after six years, indirect effects will more strongly influence diversi...